A gas buster is a simple separator vessel used to remove free or entrained gas from fluids circulated in the well bore, such as mud used during drilling operations. The gas buster typically comprises a vessel containing a series of baffles with a liquid exit on the bottom and a gas-vent line at the top of the vessel.
A buster also separates gas from mud, but it is not a sealed unit and, therefore, does not permit the pressure of the gas to increase sufficiently to enable venting to any appreciable degree. A gas buster generally vents exhaust gas immediately above the well through an eight feet vent pipe.
Separators on the other hand are used on less than five percent of all wells and only after the casings have been inserted in a well in anticipation of hitting a large quantity of gas. Gas busters are used more extensively than separators, primarily because busters are less expensive and can be constructed quickly to meet emergency situations.
It is now required that a mud-gas separator (gas buster) must be installed and operable for all operations of 10M or greater and for any operation where abnormal pressure is anticipated beginning at a point at least 500 feet above any anticipated hydrocarbon zone of interest.
During drilling mud is circulated in the borehole and the entrained gases, which can be flammable, are separated in a liquid/gas separator, also commonly referred to in the industry as a gas buster. The separated gases, also commonly specified in the industry as waste gases, exit the top of the gas buster. In some cases the gases are directed down a long pipe, which is oriented down-wind from the rig floor. This pipe is generally about 100 feet long or more and contains an ignition source at its tip. Any flammable gases, which are released from the gas buster, are burned at the tip of the flare line where the ignition source is mounted. This has been a standard set-up for drilling rigs for many, many years.
In work-over operations mud separation coming from the well bore is achieved by mounting the gas buster directly on or adjacent to a mud tank in which case mud is ejected from the bottom of the gas buster into the mud tank for recovery and the waste gas is simply vented to atmosphere rather than ignited and burned.
Virtually all live wells produce a slightly oily mist from the gas buster stack. In most cases this light liquid simply dribbles down the stack and evaporates or is collected by the mud tank. However, high winds tend to carry this oily discharge a considerable distance down-wind from the stack thereby contaminating the environment. When such operations are being carried out over water this discharge presents an even greater problem. In most cases personnel fail to report such light contamination therefore it is simply ignored.
An isolated pocket of natural gas is known as a kick if it is under control and as a blowout if it is not under control. Such kicks occur frequently thereby forcing slugs of oil out of the well at high pressure and at such a velocity that the gas buster is overwhelmed thus forcing liquids out the stack. When this happens it is considered a major spill and it cannot be ignored. High winds also contribute to the spill by taking the oily discharge great distances from the well site or into water causing extensive environmental contamination that requires expensive clean up.